PLANT PHYSIOLOGY , Vol 113, Issue 4 1059-1069, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Extracellular Matrix Assembly in Diatoms (Bacillariophyceae) (I. A Model of Adhesives Based on Chemical Characterization and Localization of Polysaccharides from the Marine Diatom Achnanthes longipes and Other Diatoms)
B. A. Wustman, M. R. Gretz and K. D. Hoagland
Department of Biological Sciences, Michigan Technological University, Houghton, Michigan 49931-1295 B.A.W., M.R.G.)
Extracellular adhesives from the diatoms Achnanthes longipes, Amphora
coffeaeformis, Cymbella cistula, and Cymbella mexicana were characterized
by monosaccharide and methylation analysis, lectin-fluorescein
isothiocyanate localization, and cytochemical staining. Polysaccharide was
the major component of adhesives formed during cell motility, synthesis of
a basal pad, and/or production of a highly organized shaft. Hot
water-insoluble/hot 0.5 M NaHCO3-soluble anionic polysaccharides from A.
longipes and A. coffeaeformis adhesives were primarily composed of
galactosyl (64-70%) and fucosyl (32-42%) residues. In A. longipes polymers,
2,3-, t-, 3-, and 4-linked/substituted galactosyl, t-, 3-, 4-, and 2-linked
fucosyl, and t- and 2-linked glucuronic acid residues predominated.
Adhesive polysaccharides from C. cistula were EDTA-soluble, sulfated,
consisted of 83% galactosyl (4-, 4,6-, and 3,4-linked/substituted) and 13%
xylosyl (t-, 4f/5p-, and 3p-linked/substituted) residues, and contained no
uronosyl residues. Ulex europaeus agglutinin uniformly localized
[alpha](1,2)-L-fucose units in C. cistula and Achnanthes adhesives formed
during motility and in the pads of A. longipes. D-Galactose residues were
localized throughout the shafts of C. cistula and capsules of A.
coffeaeformis. D-Mannose and/or D-glucose, D-galactose, and
[alpha](t)-L-fucose residues were uniformly localized in the outer layers
of A. longipes shafts by Cancavalia ensiformis, Abrus precatorius, and
Lotus tetragonolobus agglutinin, respectively. A model for diatom cell
adhesive structure was developed from chemical characterization,
localization, and microscopic observation of extracellular adhesive
components formed during the diatom cell-attachment process.
